Ensuring the Resolution field is populated before setting Status to Resolved

Ensuring the Resolution field is populated before setting Status to Resolved

Hi there,
I'm configuring our SDP (Cloud) and when creating a test ticket I noticed that I am able to resolve the ticket without anything written in the Resolution field. 
I would like to ensure that the Resolution field is populated before our Technicians are able to mark a ticket as Resolved. 
I'm sure it's probably a very straightforward setting change, but for the life of me I can't find it in the documentation I've looked through. 
Could someone please advise?
Thanks,
Amy

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